This patent application claims priority under 35 U.S.C. xc2xa7365 from International Patent Application No. PCT/GB98/03476, filed Nov. 18, 1998, which is incorporated herein by reference for all purposes.
The present invention relates to collapsible light diffusing device and to a diffused lighting apparatus incorporating such a device. The invention relates particularly, but not exclusively, to a device and lighting apparatus for use in television, film and/or video production.
Hard and soft light sources are used for a wide variety of applications in television, film and/or video production. Hard light sources, by which is meant light sources giving relatively clearly defined shadows, are generally fairly small sources in comparison with the object to be illuminated, produce relatively sharp shadows and are relatively compact, since the tungsten filaments and various types of arc lamp which are usually used are fairly compact and naturally produce very hard light.
Soft light sources, on the other hand, by which is meant more diffused light sources, need to be relatively large light sources in relation to the object to be illuminated. Soft light sources are known which are provided by placing a light diffuser between a hard light source and the object to be illuminated.
Though soft lights are by their nature large, it is desirable that these softlights should be as compact as possible for transit and storage since it should be possible to stow the light(s) along with other equipment in a vehicle such as an estate car. In addition, the equipment often must be set up in cramped conditions, for example a domestic kitchen or living room, or a small office.
Collapsible soft light sources are known which comprise a fabric shell and a hard frame of metal rods, together with a light diffuser of fabric. Such light sources are relatively compact when folded and can provide a large soft light source when assembled, but suffer from the disadvantage that the fabric shell and/or diffuser become scorched when exposed to the large amounts of heat generated by a light source, even if the fabric is xe2x80x9cflame-proofedxe2x80x9d. As a result, the light source must either be restricted in power (typically to 1000 Watts or less, although scorching is still not uncommon at such limited powers), or becomes bulky when assembled to allow adequate ventilation. Furthermore, the metal frame can become very hot during operation and requires a lengthy cooling down period, which therefore makes the light source awkward and time consuming to rig and de-rig. These light sources are typically very difficult to colour correct, with any coloured gels being applied to the front surface, which by its nature has a large area.
Preferred embodiments of the present invention seek to overcome the above disadvantages of the prior art.
According to an aspect of the present invention, there is provided a collapsible light diffusing device, the device comprising:
a collapsible housing having a folded and an unfolded condition, the housing in said unfolded condition defining a first aperture and a second aperture, larger than the first aperture, and adapted to be mounted to a light source such that said first aperture is nearer to said light source than said second aperture; and
a flexible light diffusing member adapted to cover the second aperture when the housing is in the unfolded condition thereof; wherein the housing comprises a plurality of substantially rigid panels of heat resistant material, the panels being hinged together to enable the housing to be folded between said folded and unfolded conditions.
By providing a collapsible housing formed from substantially rigid panels of heat resistant material, this give the advantage of enabling the housing to define a large diffused light source in the unfolded condition thereof, while minimizing scorching of the flexible light diffusing member by placing only heat resistant materials near to the light source.
The housing between the first and second apertures is preferably substantially light-proof when in the unfolded condition thereof.
This gives the advantage of minimizing escape of light from the device in use, thus maximizing controllability of the light emitted by the device.
The inside surfaces of the housing in use may be mirror finished to minimize light loss.
In a preferred embodiment, at least one said panel is located between the flexible light diffusing member and the components defining the first aperture when the housing is in the folded condition thereof.
This provides the further advantage of minimizing scorching of the flexible light diffusing member when the housing is in the folded condition, thus reducing the de-rigging time of lighting apparatus incorporating the device.
In a preferred embodiment, the housing has a substantially polygonal transverse cross-section in the unfolded condition thereof.
The housing preferably has a substantially octagonal cross-section in the unfolded condition thereof.
This provides the advantage of enabling the housing to have a relatively simple construction, but also to provide a large size difference between the first and second apertures whilst providing a very stable structure.
The first aperture may be substantially rectangular.
The housing preferably comprises four substantially rectangular panels, each of which is hinged to a respective side of said first aperture, and four substantially triangular panels, each of which is arranged between a respective pair of adjacent rectangular panels in the unfolded condition of the housing, and wherein each said triangular panel is hinged along one edge thereof to a respective rectangular panel.
This provides the advantage of enabling a particularly simple construction of the housing.
In a preferred embodiment, two said rectangular panels are each foldable in half and are arranged on opposite sides of said first aperture.
In a preferred embodiment, said panels are made from a carbon fiber composite.
This provides the advantage of enabling a very rigid structure of the housing while maintaining a light weight and assisting in dissipation of heat generated by a light source to which the device is mounted.
Alternatively, said panels may be made of metal.
Each said panel may be provided with a light reflecting surface.
This provides the advantage of maximizing the amount of light directed towards the light diffusing member, thus minimizing the amount of light absorbed by the panels, which would otherwise cause undesirable loss of light and heating of the panels.
The diffusing member may be formed substantially of fabric.
The diffusing member may be removably mounted to the housing.
This provides the advantage of enabling different types of diffuser member to be used on the device, or of enabling the diffusing member to be replaced when worn.
According to another aspect of the invention, there is provided a diffused lighting apparatus, the apparatus comprising a collapsible light diffusing device as defined above, and a light source arranged in use adjacent said first aperture when the housing is in the unfolded condition thereof.